US7578509B2 - Seal assembly and rotary machine containing such seal - Google Patents

Abstract

A seal assembly which, among other applications, may be used for sealing fluid leakage between a steam or combustion (gas) turbine rotor and a turbine stator body. The seal assembly includes elements having a plurality of spaced leaf seal members with slots therebetween. Each leaf seal member is angled out-of-plane between a fixed end and a free end thereof, and the free ends slidably engage the rotatable component. In one embodiment, the fixed ends of each leaf seal member are positioned substantially perpendicular to a longitudinal axis of the rotating component. A support may be provided supporting the free end such that it contacts a distal end of the support in an operative state and is out of contact with the distal end in an inoperative state. Seal members may include two different materials having different coefficients of thermal expansion.

Description

This application is a continuation-in-part application of U.S. Ser. No. 09/791,248, filed Feb. 23, 2001 now U.S. Pat. No. 6,644,667.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to seals for rotary machines and, more particularly, to a seal assembly and rotary machine containing such seal.

2. Related Art

In many rotary machines, such as a gas turbine or jet engine, a gas is compressed in a compressor and mixed with a fuel source in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stage(s) that derive energy therefrom. Both turbine stage(s) and compressor have stationary or non-rotating components, e.g., vanes, cooperating with rotating components, e.g., blades, for compressing and expanding the operational gases. The operational gases change in pressure through the machine and a variety of seals are provided to preserve the differential pressures where necessary to maximize machine efficiency and performance. An exemplary seal may be provided between a turbine rotor and a cooperating stator or stator body so the rotor may be pressurized to provide thrust balance relative to the rearwardly directed force generated by the engine and the forward direction of the engine.

In the above-described settings, turbine components and seals exceed the operating temperature range of flexible organic compound elastomer seals used in lower temperature applications. Accordingly, seals used must be capable of operation in a high temperature environment. In addition, the seals used must address the close operating clearances required in machinery of this type. Rotary machine seal design also requires consideration of the relative motion between components produced by the differential thermal expansion that occurs throughout the machinery operating cycle compared to cold clearance at assembly.

One structure commonly provided to control leakage flow along a turbine shaft or other rotating surface is a labyrinth seal. In this setting, a variety of blocking seal strips and obstructions are used between stationary turbine components. Solid labyrinth seals typically have a relatively large clearance to avoid rub damage. Labyrinth seals, therefore, do not maximize machine performance.

Another commonly used seal is a brush seal, which includes a pack of metal bristles that contact a rotor at free ends thereof to maintain a seal with the rotor. The bristles may be inclined relative to the rotor and may be supported by plates. Brush seals have been aggressively pursued in recent years to provide tighter clearances in rotating machinery seal designs because they have some resilience to accommodate rubbing against the rotating component. For instance, in U.S. Pat. No. 5,090,710, issued to Flower, a brush seal is comprised of closely packed fine wires or filaments that are weld assembled in a carrier assembly that is then inserted in a machine with the bristles wiping the rotating surface. The bristles and assembly are fabricated of materials suitable for the fluid temperature and, compared to a labyrinth seal, leakage is reduced through and past the bristles in close contact with the rotating surface.

Brush seals, however, pose a number of deficiencies. First, the multistep brush seal manufacturing process is costly. Second, brush seal bristles do not always maintain a close running clearance because of their inherent inability to withstand long term wear. Third, brush seals exposed to solid particles are subject to erosion or other deterioration. Finally, brush seals are also subject to vibration due to movement of the pressurized fluid being sealed. Therefore, brush seals oftentimes require dampening features.

Another type seal is disclosed in U.S. Pat. Nos. 5,042,823 and 5,071,138, both issued to Mackay et al. These disclosures reveal a laminated finger seal providing a planar array of radially and circumferentially extending fingers separated by gaps. This structure suffers from a number of disadvantages. For instance, each stacked lamination is a solid ring (not segmented) and, therefore, is limited in application to large diameter machines that require installation/replacement without rotor removal. In addition, the finger geometry provided is provided in a substantially radial plane, which may prevent adequate flexure of the fingers.

In addition to the above-identified problems, brush seals and finger seals operating at close running clearance are subject to rubbing and wear when differential thermal expansion of stator and rotor components eliminates clearance altogether. For example during a turbine shutdown, the stator component in which a seal assembly is mounted may cool more quickly than the rotor causing the seal assembly to close on the rotor and rub. The force imposed during such a rub is reduced somewhat with the flexure of brush and finger seal members, but sliding friction nevertheless causes wear and reduces the life of such seals

In view of the foregoing, there is a need in the art for a seal assembly having low cost manufacture and capable of withstanding the operational sensitivities described above. In addition, there is a need in the art for a seal assembly that increases seal clearance when differential thermal expansion of components closes stator to rotor separation.

SUMMARY OF THE INVENTION

In accordance with the invention a seal assembly is provided that has a number of seal members or “leaf” seals. The seal assembly may be manufactured from rolled shim stock using wire electro-discharge manufacturing (EDM) to make narrow, precision slots to produce the desired seal member geometry. The seal members may be angled between their free ends and their fixed ends and may include a support for supporting the angle. The invention provides similar benefits as brush seals and finger seals in rotary machine applications but at lower cost and with more robust attributes. Seal member geometry is engineered with respect to thickness, width, length, and number of members to meet specific application requirements of differential pressure and anticipated differential motion. The support serves to limit member movement in one direction and withstand differential pressure, while force imposed by a rub engagement on a rotating component is reduced with the elastic flexure of the seal assembly. Seal member end geometry may be shaped to provide a precision diameter and may also incorporate geometry for aerodynamic lift that would minimize wear in those rotor seal applications that anticipate a heavy transient rub.

In an alternative embodiment, the support may include a curved surface that provides a progressive gap between seal member fixed ends and their end portions under static conditions. As operating differential pressure increases across the seal assembly, leaf seal members deflect, closing the gap with the support causing their free ends to extend inward toward the rotor for a close running clearance. As a prevailing differential pressure across the seal assembly diminishes, e.g., with decreasing rotor speed during a turbine shutdown, the elastically deflected leaf seal member free ends relax and disengage from the rotor because of the leading convex face of the support. The resulting increase in clearance between seal member free ends and the rotor relieves the concurrent differential thermal expansion closure of stator and seal components, which substantially reduces or eliminates sliding friction force and wear of the leaf seal members.

In another alternative embodiment, seal assembly may include leaf seal members having their fixed portion arranged substantially perpendicular to a rotor, a free portion angled relative to the fixed portion to provide an obtuse angle to a high pressure side of the seal assembly, and a support supporting the obtuse angle on the low pressure side of the seal assembly.

In another alternative embodiment, seal assembly may include leaf seal members of bimetallic material. Bimetallic seal members changing shape in response to a change in temperature can relieve the affects of a seal rub when bimetallic seal members are arranged to disengage from the rotor with increasing temperature. Frictional heating during a seal rub increases bimetallic seal member temperature as contact is made with the rotor causing the free portions of the seal members to curl away from the rotor thereby reducing applied rub force and associated wear.

In a first aspect of the invention is provided a seal assembly comprising: a leaf seal including a plurality of staggered leaf seal members, the leaf seal including a fixed portion that is angled relative to a free portion thereof; and a support coupled to the leaf seal for supporting the free portion, the support having a support portion facing a high pressure side of the leaf seal, wherein the free portion contacts a distal end of the support portion in an operative state and is out of contact with the distal end in an inoperative state.

A second aspect of the invention provides a seal assembly for sealing against a rotatable component, the seal assembly comprising: a leaf seal including a plurality of leaf seal members, the leaf seal including a fixed portion that is angled relative to a free portion thereof; and wherein the fixed portion is positioned substantially perpendicular to a longitudinal axis of the rotatable component, and the free portion is, in an inoperative state, angled out-of-plane relative to the fixed portion and slidably engages to seal against the rotatable component at an angle relative to the longitudinal axis in an operative state.

In a third aspect of the invention is provided a rotary machine comprising: a rotatable component and a non-rotatable component, the components lying about a common axis; a seal assembly between the components, the seal assembly including: a leaf seal including a plurality of staggered leaf seal members, the leaf seal including a fixed portion that is angled relative to a free portion thereof; and a support coupled to the leaf seal for supporting the free portion, the support having a support portion facing a high pressure side of the leaf seal, wherein the free portion contacts a distal end of the support portion in an operative state and is out of contact with the distal end in an inoperative state.

In a fourth aspect of the invention is provided a method of fabricating a seal assembly for sealing pressurized chambers of a rotary machine having a stator body and a rotor, the method comprising the steps of: (a) forming a leaf seal including a plurality of leaf seal members, the leaf seal including a fixed portion that is angled relative to a free portion thereof in an inoperative state; and (b) coupling the leaf seal to a support, including a support portion, such that the free portion contacts a distal end of the support portion in an operative state and is out of contact with the distal end in the inoperative state.

A fifth aspect of the invention is directed to a support for use with a leaf seal having a fixed portion and a free portion angled relative to the fixed portion, the support including: a mount portion for mounting the fixed portion; and a support portion for supporting the free portion of the leaf seal, the support portion including a proximate end that contacts the free portion in an operative state and an inoperative state of the leaf seal, and a distal end that contacts the free portion in an operative state and is out of contact with the distal end in an inoperative state of the leaf seal.

A sixth aspect of the invention is directed to a seal assembly comprising: a leaf seal including a plurality of staggered leaf seal members, the leaf seal including a fixed portion that is angled relative to a free portion thereof; and a support coupled to the leaf seal for supporting the free portion, wherein each leaf seal member includes a first layer including a first material addressing a high pressure side of the leaf seal and a second layer of a second material addressing a low pressure side of the leaf seal, wherein the first material has a lower coefficient of thermal expansion than the second material.

The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of this invention will be described in detail, with reference to the following figures, wherein like designations denote like elements, and wherein:

FIG. 1 shows a rotary machine including a first embodiment of a seal assembly in accordance with the present invention;

FIG. 2 shows a rotary machine including a number of arcuate seal assemblies;

FIG. 3 shows a cross-sectional view of the first embodiment of the seal assembly ofFIG. 1;

FIG. 4 shows a cross-sectional view of a second embodiment of the seal assembly;

FIG. 5 shows a detail view of a first embodiment of seal members of an element of the seal assembly;

FIG. 6 shows a detail view of a second embodiment of seal members of an element;

FIG. 7 shows a detail view of a third embodiment of seal members of an element;

FIG. 8 shows a detail view of a fourth embodiment of seal members of an element;

FIG. 9 shows a detail view of a fifth embodiment of seal members of an element;

FIG. 10 shows a partial detail view of an element mounted adjacent a rotating component of a rotary machine;

FIG. 11 shows a detail view of a number of elements configured with staggered slots;

FIG. 12 shows a detail view of a number of elements configured with non-staggered slots;

FIG. 13 shows a detail view of a seal member including alternative surfaces for mating with a rotating component of a rotary machine;

FIG. 14A-B show a side view and a detail view of a first embodiment of a method of fabrication of the seal assembly;

FIG. 15 shows a detail view of seal member slot cutting according to the method of fabrication;

FIG. 16 shows a detail view of the seal assembly shown inFIG. 3 prior to formation of a seal member angle;

FIG. 17 shows a detail view of angle formation of the seal assembly shown inFIG. 3;

FIG. 18 shows a detail view of the seal assembly shown inFIG. 4 prior to formation of the seal member angle;

FIG. 19 shows a detail view of angle formation of the seal assembly shown inFIG. 4;

FIGS. 20A-B show a side view and a detail view of a second embodiment of a method of fabrication of the seal assembly;

FIGS. 21A-C shows cross-sectional views of operational states of a third embodiment of the seal assembly;

FIG. 22 shows a cross-sectional view of a fourth embodiment of the seal assembly;

FIG. 23 shows a detail view of the fourth embodiment ofFIG. 22; and

FIGS. 24A-B show cross-sectional views of operational states of a fifth embodiment of the seal assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 1 and 2, the present invention provides aseal assembly10 for use with arotary machine12.Rotary machine12 may be any well known machinery that includes anon-rotating component14 and arotating component16 having alongitudinal axis15, e.g., a gas turbine, a jet engine, a steam turbine, etc. For description purposes, the present invention will be described in terms of a steam or combustion (gas) turbine having a stator orstator body14 and arotor16. As shown inFIG. 1, a higher pressure chamber P_Hand a lower pressure chamber P_Lare generated during steady state operation ofrotary machine12. Pressure from higher pressure chamber P_His exerted against at least part ofseal assembly10, which acts to seal higher pressure chamber P_Hfrom lower pressure chamber P_L.FIG. 2 shows an embodiment of rotary machine where a number ofarcuate seal assemblies10 are utilized about rotatingcomponent16.

Turning toFIGS. 3 and 4,seal assembly10 includes at least afirst element20 and asecond element22, and preferably three ormore elements20,22.Elements20,22 are layered together (juxtaposed) and carried bynon-rotating component14.Elements20,22 are preferably made of a heat resistant material, e.g., a nickel-based or cobalt alloy material.Elements20,22 also have a thickness, width, length and number set to meet application requirements such as differential pressure and differential motion of the particularrotary machine12 at issue. In a preferred embodiment,elements20,22 are coupled to aholder18 that is coupled tonon-rotating component14. Eachseal assembly10 is preferably provided as an arcuate structure such that a number ofseal assemblies10 can be circumferentially disposed about rotatingcomponent16 to create a seal. In this case, as shown inFIGS. 1,3 and4,holder18 is preferably non-rotatably held in akey slot19 ofnon-rotating component14 that is concentric withrotating component16. As an alternative embodiment, however, sealassembly10 may be provided as an annulus andelements20,22 may be provided by a spiral of a single strip of material. While a particular structure has been disclosed for holdingseal assembly10, it should be recognized that a number of other mechanisms of mountingseal assembly10 tonon-rotating component14 may be possible.

FIG. 5 illustrates how eachelement20,22 includes a plurality of spacedleaf seal members24 havingslots26 therebetween. Eachseal member24 includes a fixed end orportion28 and a free end orportion30. While a variety of mechanisms may be used to fix ends28, preferably eachfixed end28 is provided by forming sealedmembers24 integrally with aband portion32 of eachelement20,22. Once assembled,band portions32 of eachelement20,22 are preferably coupled to form a single band portion to prevent relative motion of theelements20,22 by welding at or near fixed ends28 of eachseal member24. Aweld36 may be provided throughelements20,22 and a support38 (FIGS. 3,4)(discussed below) to couple them toholder18.Weld36 may be provided as, for example, a laser or electron beam weld.

As illustrated inFIGS. 5-9,slots26 may be provided in a variety of shapes and dispositions inelements20,22. InFIG. 5,slots26 are provided inelements20,22 such that they extend substantially perpendicular to free ends30.FIG. 6 illustratesslots26 that extend at a substantially non-perpendicular angle relative to free ends30.FIGS. 7 and 8 illustrateslots26 that diverge at least partially from fixedend28 tofree end30. A divergent configuration may be advantageous whereseal members24 interfere with one another whenseal assembly10 is mounted, e.g., on a smallrotatable component16. For instance, as shown inFIG. 10, when aseal assembly10 is mounted,elements20,22 are arced such thatseal members24 converge at their free ends30. Divergent slots may prevent interference between free ends30 ofadjacent seal members24. InFIG. 7,slots26 are V-shaped, and inFIG. 8,slots26 are funnel-shaped.FIG. 9 illustrates thatseal members24 do not have to be uniformly spaced in eachelement20,22. That is,seal members24 may have different circumferential widths.

Turning toFIG. 11,slots26 may also be provided at a non-perpendicular angle relative to asurface25 of eachelement20,22.FIG. 11 also illustrates how, in a preferred embodiment,slots26 ofelements20,22 are staggered betweenelements20,22. That is,elements20,22 are preferably juxtaposed such thatseal members24 of eachelement20,22block slots26 of anotherelement20,22. This configuration reduces leakage throughseal assembly10. However, as an alternative embodiment, shown inFIG. 12,slots26 can be provided in a non-staggered or aligned disposition betweenelements20,22. This may be advantageous where a certain amount of leakage between chambers P_Hand P_Lis acceptable or desired.FIG. 12 also illustrates another alternative embodiment in whichseal assembly10 is constructed of a number ofelements20,22 that are not of uniform axial thickness.

Returning toFIGS. 3 and 4, each seal member also preferably includes an angle α between their respective fixedend28 andfree end30 thereof. The inwardly-extending angle α results in fixedend28 being arranged at a non-perpendicular angle relative to a longitudinal axis ofrotatable component16 andfree end30 being arranged at an angle relative to fixedend28 and towardrotatable component16. The bend location of angle α is indicated inFIGS. 5-9 asline34.FIG. 3 illustrates an angle α of approximately 135 degrees, which presentsseal members24 at approximately 45 degrees relative torotating component16.FIG. 4 illustrates an angle α of approximately 90 degrees, which presentsseal members24 at approximately 90 degrees, i.e., radial, relative torotating component16. It should be recognized that while two preferred angles have been presented, angle α may be set at any other angle that is necessary for the specific design in issue.Seal assembly10 may also include asupport38 for supporting the angle α andseal members24.Support38 preferably bears a substantial portion of the seal assembly's differential pressure with minimal distortion during normal operating conditions. In either seal assembly configuration, angle α andsupport38 provide relief betweenseal members24 andholder18. This relief functions to accommodate relative motion betweennon-rotating component14 and rotatingcomponent16 whenseal members24 rub on rotatingcomponent16. Since the full length ofseal member24 may be deflected during such a rub, the seal member tip (free end) force on rotatingcomponent16 is reduced. As mentioned above, aweld36 may be provided throughelements20,22 andsupport38 to coupleelements20,22 toholder18.

Referring toFIG. 10, as an alternative embodiment, eachseal member24 may also include acircumferentially extending notch40 at their respective free ends30. In a preferred setting, eachnotch40 faces a direction of rotation, indicated by arrow A, ofrotatable component16. A circumferentially extendingmating notch42 may also be provided in an opposite side of eachfree end30.Notches40 are advantageous, inter alia, to provide aerodynamic lift to minimize wear in those applications that anticipate a heavy transient rub. This situation may exist, for instance, whereslots26 are not staggered betweenelements20,22.

Another alternative embodiment is illustrated inFIG. 13, in which thefree end30 of eachseal member24 is formed to mate with a surface of rotatingcomponent16. For example, free ends30 may be formed or cut to include an angle β such thatfree end30 is axially parallel a surface ofrotatable component16 when in operation. Angle β may be substantially similar to angle α. An additional alternative embodiment, shown inFIG. 13, includes having thefree end30 of eachseal member24 formed to be circumferentially parallel a surface ofrotatable component16. In this case,free end30 of each seal member is formed or cut to a radius R to substantially mimic an outer diameter of rotatingcomponent16.

It should be recognized that theseal assembly10 in accordance with the present invention may be combined with one or more labyrinth seals and/or one or more brush seals (not shown) to provide further sealing capacity.

In operation, as shown inFIG. 1,seal assembly10 is carried bynon-rotating component14 in such a way that free ends30 ofseal members24 slidably engage rotatingcomponent16. As one with skill in the art will recognize, cold assembly ofseal assembly10 androtary machine12 may require non-contact of parts to accommodate eventual thermal expansion.Seal assembly10 creates a seal between chambers P_Hand P_Landseal members24 resist flexure in one direction by the provision of angle α andsupport38.

Referring toFIGS. 14-19, a first preferred embodiment for the fabrication ofseal assembly10 is illustrated. As shown inFIGS. 14A-B, a strip ofmaterial100, preferably ribbon shim stock, of requisite thickness, width and material is first layered. Layering is preferably provided by winding strip ofmaterial100 onto amandrel102 to form an annulus having a number of layers needed for a particular seal design.Mandrel102 is preferably annular and has an outer diameter that is sized such that the outside diameter of the roll ofmaterial104 once completed corresponds to an inside diameter of holder18 (FIG. 1) or other structure to whichseal assembly10 is connected.

Next, roll ofmaterial104, part of which is shown inFIG. 15, is preferably transferred to afixture103, e.g., a ring fixture, for support. While supported onfixture103,slots26 are cut in an edge ofmaterial104 to form the plurality ofseal members24 coupled to aband portion32.Slots26 extend through the thickness of roll ofmaterial104. A preferred method of cuttingslots26 is using wire electro-discharge machining (EDM)106 (shown conceptually).EDM106 has been found advantageous because it does not raise a burr, can produce narrow slots (e.g., down to 0.002 inches), utilizes computer controlled positioning to readily produce complex shapes, and does not involve heavy tool force. It should be recognized, however, that other mechanisms of creatingslots26 may also be used. Furthermore,mandrel102 may be so structured that the transfer of roll ofmaterial104 may not be necessary.

As discussed above with reference toFIGS. 5-9,slots26 may be provided in a variety of different shapes. For example, as illustrated inFIG. 15,slots26 may be cut perpendicular relative to asurface25 ofelements20,22 (i.e., along line106) and extend substantially perpendicular to free ends30, i.e., radially relative torotating component16, once assembled. Alternatively,slots26 may be cut at a non-perpendicular angle relative to surface25 ofelements20,22, i.e., alongline108.Wire EDM106 is capable of producing any slot geometry, shown inFIGS. 5-9, or other combination of geometries as may be required for a specific seal design.

If staggering ofslots26 is desired, it is preferably provided next by re-layering roll ofmaterial104 such thatseal members24 of each element/layer block at least oneslot26 of another element/layer. Re-layering is preferably provided by winding roll ofmaterial104 onto a mandrel (not shown) having different dimensions thanmandrel102, which repositionsslots26 to the desired staggered configuration. In this way, leaf seal members of one revolution block slots of at least one other revolution.

Next, a consolidation of roll ofmaterial104 is provided by, for example, resistance welding105 roll ofmaterial104 through an edge of the roll of material that does not includeslots26, i.e.,band portion32. In this setting, whatever structure is supporting roll ofmaterial104, e.g.,mandrel102 orfixture103, may be made of, or coated with, a suitable material (not shown) to facilitate complete consolidation through roll ofmaterial104.

Referring toFIGS. 16-19, the next step of fabrication is to form angle α in eachseal member24. As indicated above, seal members may be provided with an angle α of, for example, approximately 135° or of approximately 90°. As illustrated inFIGS. 16-19, one method of providing angle α is to clamp110 slotted roll ofmaterial104 to amandrel112,212. Mandrel112 (FIGS. 16 and 17) provides the approximately 135° angle and mandrel212 (FIGS. 18 and 19) provides the approximately 90° angle. In the case ofmandrel112, forming angle α results in an inwardly frusto-conically shaped portion having the plurality of spacedleaf seal members24 withslots26 therebetween that is coextensive withband portion32 and extends inwardly fromband portion32 towardsrotatable component16. In either case, the slottedmaterial104 is secured to a mandrel with geometry needed to form angle α inseal members24. Consideration for material properties that affect spring back frommandrel112,212 shape should be anticipated in choosingmandrel112,212. Forcingseal members24 to conformity withmandrel112,212 would include those techniques applied in sheet metal fabrication such as peening or rolling, but may include pressure forming, hydrostatic forming, explosive forming or any other now known or later developed technique.

Next, referring toFIG. 1,band portions32 are coupled tonon-rotating component14, e.g., a stator body, ofrotary machine12. As discussed above,elements20,22 andsupport38 are preferably welded toholder18, which is coupled tonon-rotating component14.Seal members24 are mounted in such as way that they slidably engage rotatingcomponent16 ofrotary machine12, when in operation, to seal the pressurized chambers P_Hand P_L. In a preferred embodiment,holder18 is an annulus with a cross-sectional geometry capable of mounting either of seal assembly configuration discussed above. Compatible structure, e.g.,key slot19, forholder18 is provided innon-rotating component14 in a known fashion to maintain seal concentricity withrotating component16 andsecure holder18 from rotation.

An alternative step to the above-described process may include separating roll ofmaterial104 after connection toannular holder18 into arcuate segments so that a number ofseal assemblies10 may be circumferentially arranged about rotatingcomponent16, as shown inFIG. 2. Segmentation ofseal assembly10 is advantageous for shipping, handling and assembly requirements. In addition,segmented seal assemblies10 makes replacement easier. Segmentation is preferably provided by making radial, narrow kurf cuts by wire EDM in roll ofmaterial104 andannular holder18. As with an annular seal assembly, provisions for anti-rotation of arcuate seal assemblies, such as those used in brush seal applications, may be provided to complete the fabrication.

Another alternative step includes forming free ends30 ofseal members24 to conform to a surface of rotatingcomponent16, as shown inFIG. 13. That is, shape free ends30 to be axially parallel a surface ofrotatable component16 and/or circumferentially parallel a surface ofrotatable component16. Furthermore,notches40,42 may be provided at this stage whereslots26 are not staggered. Precise numerical control of the wire EDM operation can accommodate the above features.

Referring toFIG. 20, an alternative embodiment of the method of fabrication is illustrated in which the step of cuttingslots26 into an edge of the strip ofmaterial100 precedes the step of layering the strip ofmaterial100. In this approach, a strip ofmaterial100 is provided from a stock ofmaterial120 and is slotted one individual layer at a time as it is fed through anEDM machine122. Any of the slot geometries discussed above may be provided byEDM machine122. The slotted material is then wound on amandrel202, as described above, to produce a roll ofmaterial204 having an outer diameter that corresponds to an inner diameter ofholder18 or other structure to whichseal assembly10 is to be mounted.

This method can also automatically produce multiple layers ofelements20,22 that have staggeredslots26 as shown in the enlarged view of roll ofmaterial204, shown inFIG. 20B. That is,elements20,22 are juxtaposed such that seal members of each element/layer block slots of another element/layer.

The rest of the process of fabrication in accordance with the second preferred embodiment is substantially similar to that of the first embodiment.

The present invention also includes a method of inhibiting fluid flow through an annular slot (i.e., chambers P_Hand P_L) defined between astator body14 and arotor16 received in thestator body14, the rotor having longitudinal axis15 (FIG. 1), the method including the steps of: disposing on the stator body14 a plurality ofarcuate elements20,22 each having aband portion32 and an integral plurality of circumferentially disposedseal members24 havingslots26 therebetween, wherein theseal members24 includes an angle α therein and extend inwardly from the stator body at an angle relative to the longitudinal axis toslidably contact rotor16 along a circumference thereof; circumferentially aligning and axially juxtaposingelements20,22; employing the cooperatively disposedelements20,22 to define an annular seal extending between thestator body14 and therotor16; and inhibiting fluid flow through the annular slot with the annular seal.

Referring toFIG. 21A, as an alternative embodiment, a seal assembly310 may include aleaf seal311 including a plurality of staggered leaf seal members324 similar to those described above.Leaf seal311 includes a fixedportion328 and a free portion330. Seal assembly310 also includes asupport338 having amount portion346 and asupport portion348, the latter of which faces a high pressure side P_Hofleaf seal311.Mount portion346 couples support338 to a stationary component314.Support portion348 is coupled toleaf seal311 for supporting free portion330.

FIG. 21A illustrates the position of free portion330 during an inoperative state with low or no differential pressure P_H−P_Land with a clearance Cl1 between free portion330 androtating component316.FIG. 21B shows the position of free portion330 during a hot, running operative state (FIG. 21B) with high operating conditions' differential pressure, P_H−P_L, and with a clearance Cl2 between free portion330 androtating component316. ComparingFIGS. 21A and 21B, in one embodiment, free portion330 is out of contact with adistal end354 ofsupport portion348 in the inoperative state (FIG. 21A), and contactsdistal end354 in an operative position (FIG. 22B). Thermal expansion and centrifugal growth ofrotating component316 also contributes to reduced seal clearance as illustrated inFIG. 21B. In one embodiment, free portion330 is formed at a cold-relaxed angle α relative to fixedportion328, andsupport338 includes acurved surface360 extending from aproximate end352 todistal end354 ofsupport portion348 such that free portion330 extends tangentially fromcurved surface360 at apoint351 in an inoperative state.FIG. 21C shows an intermediate state in which differential pressure, P_H−P_L, is diminished and leaf seal free portion330 elastically disengages fromrotor316 as illustrated by increased clearance Cl3 compared to clearance Cl2 inFIG. 21B.

The shape ofcurved surface360 is chosen in cooperation with leaf seal member324 length, L, and thickness, T, to have free portion330 extend tangentially fromcurved surface360 in an inoperative state, i.e., cold state, such that free portion330 is disengaged from a majority ofsupport portion348, as shown inFIG. 21A. In addition,curved surface360 is chosen to attain a desired elastic flexure of free portion330 inward towardrotating component316 and into engagement withsupport portion348 at operating conditions, as shown inFIG. 21B in which running clearance Cl1 is very small. The change in clearance created by this structure can be made large enough to disengage or distance free portion330 sufficiently to avoid rubbing contact withrotating component316 as applied differential pressure, P_H−P_L, diminishes.

Although the structure ofsupport portion348 that provides for the tangential extension of free portion330 has been described as a “curved surface,” it should be recognized that a variety of other functionally equivalent structure(s) may be provided to create the above-described operation. For instance,distal end354 ofsupport portion348 may be constructed to simply be thinner thanproximate end351;support portion348 may be constructed to include a number of planar surfaces that, in combination, form a functional equivalent tocurved surface360; orsupport portion348 may include a ridge that supports free portion330 in a tangentially extending fashion. Whencurved surface360 is provided, it may be formed to a particular contour radius ρ (FIG. 21B). In this case, seal member bending stress σ equals E*T/2ρ to ensure seal member324 elastically deflect into contact withsecond portion348 ofsupport338 by applied operating differential pressure, P_H−P_L. In the equation, T is seal member324 thickness, and E is the modulus of elasticity of the seal member material. An illustrative material is heat resistant sheet metal such as AMS 5537 (Haynes 25 alloy or alloy L-605). Typical tensile properties of this material when cold worked and aged include 0.2% yield strength in excess of 120,000 psi at temperatures between 600° F. and 1000° F. A contour radius ρ of, for example, 1.3 inch induces bending stress that is within AMS5537 yield stress for seal members up to 0.010 inches in thickness.

It is recognized that contour radius p insupport portion348 creates a three-dimensional surface of revolution and that seal members324 may not be compliant along the arc subtended by individual seal members and some stress concentration will occur. Parts of free portion330 extending belowdistal end354 ofsupport portion348 are exposed to differential pressure without support, inducing additional cantilever bending stress. To assure seal members324 elastically return to original shape at shut down, the sum of cantilever bending stress and contour bending stress must not exceed material yield stress. Attention is also given to the selection of seal member length L, along with thickness T, and the number of cooperating seal member324 layers that will bring seal members324 into elastic contact withsupport portion348 ofsupport338 under operating differential pressure without excessive contact force. In such a design, seal members324 promptly respond to reduced differential pressure and elastically spring fromsupport portion348 ofsupport338 toward their original shape and approximate cold clearance.

Referring toFIGS. 22-23, another alternative embodiment of aseal assembly410 is shown. As shown inFIG. 22,seal assembly410 includes aleaf seal411 including a plurality ofleaf seal members424 made, for example, ofelements420,422 that each include a plurality ofleaf seal members424. Each two adjacentleaf seal members424 have aslot426 therebetween as shown inFIG. 23. In this embodiment, however, eachleaf seal member424 is formed with an arcuate, planar fixed portion428 such that the fixed portion may be layered in a position substantially perpendicular to a longitudinal axis of a rotating component416 (FIG. 22) to form the seal assembly. Afree portion430 of eachleaf seal member424, in the inoperative state is angled out-of-plane relative to its fixed portion428 and slidably engagesrotatable component416 at an angle relative to the longitudinal axis thereof during operation to seal.

As shown inFIG. 22,support438 functions similar to support338 as previously discussed. In this case,support438 includes an arcuate mount portion446 (into and/or out of page) compatible with arcuate fixed end428, e.g., substantially perpendicular to longitudinal axis ofrotatable component416, and an arcuate support portion448 (into and/or out of page) compatible withfree portion430. As an alternative,support portion448 ofsupport438 may include acurved surface460 similar to that described relative toFIGS. 21A-C. Aweld436 may be provided throughelements420,422 andsupport438 to couple them to aholder418.Holder418 is keyed tonon-rotating component414 similar to holder18 (FIG. 1). In one embodiment,holder418 may be provided with aprojection480 having a diameter that is only slightly larger than a diameter of seal memberfree portion430 such thatholder418 provides a measure of protection forseal elements420,422, for example, during shipping and installation.

The invention may also include a method of fabricating a seal assembly310,410 (FIGS.21AC,22, respectively) for sealing pressurized chambers of a rotary machine having astator body314,414 and arotor316,416 comprising the steps of: (a) forming aleaf seal311,411 including a plurality ofleaf seal members324,424, theleaf seal311,411 including a fixedportion328,428 that is angled relative to afree portion330,430 thereof in an inoperative state; and (b) coupling theleaf seal311,411 to asupport338,438, including asupport portion348,448, such thatfree portion330,430 contacts adistal end354,454 of thesupport portion348 in an operative state (FIG. 21B,22) and is out of contact with the distal end in the inoperative state (FIG. 21A,22). With regard to the step of forming and theFIGS. 22-23 embodiment, eachelement420,422, i.e., fixed portion428, is preferably an arcuate member. However, eachelement420,422 may be formed from a planar annulus476 (only a portion shownFIG. 23 for clarity), i.e., each fixed end428 is one integral member.Seal assembly410 is fabricated usingseal elements420,422 having a plurality ofleaf seal members424 formed by cuttingslots426 radially into aninner edge478 of annulus (or arcuate member)476 similar to seal members24 (FIGS. 5-9), as previously discussed.Slots426 may be provided in a variety of shapes and dispositions similar to those shown inFIGS. 5-9. Eachseal member424 includes a fixed end428 and a free end orportion430. Free ends430 are provided by formingseal members424 integrally from arcuate fixed portion428 of eachelement420,422. A plurality ofannuluses476 may then be layered, and then have an angle formed therein, e.g., by bending. The step of layering, however, may precede the cutting step described above. Layering may also include positioningleaf seal members424 such that leaf seal members of eachlayer block slots426 of another layer. The location of an angle α as indicated inFIG. 22 can be formed along anarc434 as shown inFIG. 23. An appropriate mandrel (not shown) will include the proper arcuate surface to form angle α fromelements420,422 having arcuate, planar fixed end428. The layers of annuluses may then be coupled to asupport438.

With continuing reference toFIGS. 21A-23, the invention may also include asupport338,438 for use with aleaf seal311,411 having a fixedportion328,428 and afree portion330,430 angled relative to the fixed portion. The support includes amount portion346,446 for mounting fixedportion328,428; and asupport portion348,448 for supportingfree portion330,430 of the leaf seal, the support portion including aproximate end352,452 that contacts the free portion in an operative state and an inoperative state of the leaf seal, and adistal end354,454 that contacts the free portion in an operative state and is out of contact with the distal end in an inoperative state of the leaf seal.

Referring toFIG. 24A, as an alternative embodiment, aseal assembly510 may include aleaf seal511 including a plurality of staggeredleaf seal members524 ofelements520,522 with similar geometry to those described above but fabricated from a bimetallic material.Seal assembly510structure including support538,holder518,weld536 androtor516 are similar in form and function to seal assembly embodiments discussed above. With regard to the bimetallic material,FIG. 24A inset, shows bimetallic cross section ofseal member524. Eachleaf seal member524 includes afirst layer570 of a first material addressing high pressure P_Hside ofseal member524, and asecond layer572 of a second material addressing low pressure P_Lside ofseal member524. In one embodiment, first material has a lower coefficient of thermal expansion (CTE₁) than second material (CTE₂).First layer570 is bonded tosecond layer572 in any now known or later developed fashion. An increase in bimetallic leaf seal temperature induces a change in shape causingseal members524 to curl upward, increasing clearance withrotor516.FIG. 24A illustrates normal operation with the extremities offree portion530 andbimetallic seal members524 in close proximity, C1, withrotor516. Elevated operating temperature tends to curlseal members524 upwardly. This movement is opposed by differential seal pressure, P_H−P_L, which tends to displaceseal members524 towardsupport member538 androtor516. InFIG. 24Bfree portions530 are in rubbing contact withrotor516, and a separation ofsupport538 fromrotor516 is at a distance D1, which is reduced compared to distance D2 inFIG. 24A. As frictional heating ofbimetallic seal members524 occurs, increased temperature induces additional shape change to liftseal members524 fromrotor516 relieving imposed rub force and further frictional heating, as illustrated by increased curvature ofseal members524 inFIG. 24B. In combination,metallic materials570,572 (i.e., via the different coefficients of thermal expansion and other physical properties), operating differential pressure P_H−P_L, leaf seal thickness, length, strength, and the cooperation withsupport member538, act to relieve wear during a rub and extend a leaf seal's ability to operate under less extreme operational situations.Support538 may also include a curved surface560, similar to that shown inseal assembly410 inFIG. 21A.

With further regard to the embodiments ofFIGS. 21A-24B,leaf seal members324,424,524 may be cut or formed in any manner described relative to the earlier embodiments. For example,leaf seal members330,430,530 may be formed to comply withrotatable component316,416,516 when in operation as previously described and illustrated inFIG. 13. That is,free portion330,430,530 of each seal member may be axially parallel and/or circumferentially parallel a surface ofrotatable component316,416,516. In addition, leaf seal members may be non-uniformly spaced; have diverging slots; have respective elements juxtaposed such that seal members of each element block slots of another element; and/or have slots that are provided at an angle relative to a surface of each element.

While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims (14)

1. A seal assembly for sealing against a rotatable component having a longitudinal axis, the seal assembly comprising:

a leaf seal including a plurality of staggered leaf seal members, each leaf seal member including:

a free portion arranged at an acute angle relative to the longitudinal axis of the rotatable component, and

a fixed portion that is angled relative to the free portion; and

a support having a substantially frusto-conically shaped support portion facing a high pressure side of the leaf seal for supporting the free portion from a radially inward position relative to the free portion and a mount portion for coupling to a non-rotatable component,

wherein the free portion contacts only a proximate end of the support portion adjacent to the mount portion in an unpressurized state of the leaf seal and the free portion contacts both the proximate end and a distal end of the support portion in a pressurized state of the leaf seal, the free portion being closer to the rotatable component during the pressurized state than in the unpressurized state.

2. The seal assembly ofclaim 1, wherein each leaf seal member includes a first layer including a first material addressing a high pressure side of the leaf seal and a second layer of a second material addressing a low pressure side of the leaf seal, wherein the first material has a lower coefficient of thermal expansion than the second material.

3. The seal assembly ofclaim 1, wherein the support portion includes a curved surface extending from the proximate end of the support portion to the distal end.

4. The seal assembly ofclaim 3, wherein the free portion extends tangentially from the curved surface in the unpressurized state.

5. The seal assembly ofclaim 1, wherein the plurality of staggered leaf seal members are provided by a spiral of a single strip of material.

6. The seal assembly ofclaim 1, wherein the plurality of staggered leaf seal members are fixed together at the fixed portion by a weld.

7. The seal assembly ofclaim 1, wherein the fixed portion is positioned substantially parallel to a radial axis of the non-rotatable component, and the free portion is angled out-of-plane relative to the fixed portion.

8. The seal assembly ofclaim 1, wherein the distal end of the support portion is thinner than the proximate end of the support portion.

9. The seal assembly ofclaim 1, further comprising a holder for mounting the seal assembly to the non-rotatable component, wherein the holder includes a projection for protecting the free portion.

10. The seal assembly ofclaim 1, wherein the fixed portion is provided by an arcuate member in each leaf seal member.

11. A rotary machine comprising:

a rotatable component and a non-rotatable component, the components lying about a common axis;

a seal assembly between the components, the seal assembly including:

a leaf seal including a plurality of staggered leaf seal members, each leaf seal member including:

a free portion arranged at an acute angle relative to the longitudinal axis of the rotatable component, and

a fixed portion that is angled relative to the free portion; and

a support having a substantially frusto-conically shaped support portion facing a high pressure side of the leaf seal for supporting the free portion from a radially inward position relative to the free portion and a mount portion for coupling to the non-rotatable component,

wherein the free portion contacts only a proximate end of the support portion adjacent to the mount portion in an unpressurized state of the leaf seal and the free portion contacts both the proximate end and a distal end of the support portion in a pressurized state of the leaf seal, the free portion being closer to the rotatable component during the pressurized state than in the unpressurized state.

12. The rotary machine ofclaim 11, wherein each leaf seal member includes a first layer including a first material addressing a high pressure side of the leaf seal and a second layer of a second material addressing a low pressure side of the leaf seal, wherein the first material has a lower coefficient of thermal expansion than the second material.

13. The rotary machine ofclaim 11, wherein the support portion includes a curved surface extending from the proximate end to the distal end.

14. The rotary machine ofclaim 11, wherein the distal end of the support portion is thinner than the proximate end of the support portion.

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